The present invention relates to transmitter circuits and systems, and more particularly to ultra wideband transmitter circuits and systems.
Ultra-wide band (UWB) is a new and promising technology for high speed, short range and portable wireless communication systems and devices. UWB technology enables new opportunities in the development of short range and high data rate wireless communication applications such as wireless Personal Area Network (PAN), interactive gaming, office networking and indoor communications.
The design of the building blocks of the UWB wireless transceiver is very demanding due to its simultaneous requirements for ultra-wide bandwidth, high speed, high throughput, low interference and low power consumption. Critical to operation is the generation of vary narrow pulses (typically 0.2-2 nano-seconds) onto which information is modulated. It is extremely difficult to generate sub-nanosecond pulses in pulse generator/modulator circuits whether the circuit be formed either from discrete components due to interconnection discontinuities, and capacitive coupling between components, or in an integrated circuit due to the low isolation and low current gain of the complementary metal oxide semiconductor (CMOS) or bipolar-complementary metal oxide semiconductor (BiCMOS) processes.
Furthermore, the pulse generator/modulator output is often times too low to drive the antenna, and accordingly a matching network is many times necessary to provide optimal impedance matching to the UWB antenna. Typically however, the matching circuit is not as broadband as the UWB spectrum (e.g., 3.1-10.6 GHz in the U.S), and thus power loss due to impedance mismatch occurs over some part of the transmission band. Additionally, broadband matching networks are typically quite lossy, and thus provide diminishing returns on bandwidth versus output power.
Accordingly, a need exists for improved UWB transmitter circuits and systems, and which are preferably capable of monolithic integration using CMOS or BiCMOS semiconductor processes.